Polymer product containing isobutylene oxide polyols

ABSTRACT

Novel polyether polyols are disclosed which contain an internal block of isobutylene oxide or a mixture of isobutylene oxide and a mono- or unsaturated alkylene oxide and an end-cap of a mono- or unsubstituted alkylene oxide to provide reactive primary or secondary hydroxyl end-groups. The polyether polyols are useful intermediates in the production of segmented elastomers. A process for the preparation of the novel polyols is also described in which an alkali metal catalyst and a crown ether cocatalyst are employed to afford polyols containing relatively low levels of unsaturation.

This is a division of application Ser. No. 07/310,187 filed on Feb. 14,1989, now U.S. Pat. No. 5,003,111.

This invention relates to novel polyethers containing isobutylene oxide.More particularly, this invention pertains to isobutylene oxidepolyether polyols having hydroxyl end-groups which are predominantlyprimary or secondary and which render the polyether polyols reactivetowards electrophilic functional groups.

BACKGROUND OF THE INVENTION

Polyether polyols are useful as intermediate in the preparation ofpolyurethanes. In addition, polyether polyols are commonly used directlyin other applications and may be employed as functional fluids andsurfactants, for example.

Typically, polyether polyols are prepared by polymerizing a mono- orunsubstituted alkylene oxide such as ethylene oxide, propylene oxide, or1,2-butylene oxide using base catalysis or by polymerizing an oxolanesuch as tetrahydrofuran using acid catalysis. The properties of thepolyether polyols may be controlled by varying the chemical structure ofthe monomers, the order and arrangment of the monomers in the polyol,the polyol molecular weight, and the average functionality of thepolyol.

To date, only a limited variety of polyether polyols containingisobutylene oxide, a di-substituted alkylene oxide, have been prepared.This is due to the difficulties associated with polymerizing thismonomer while retaining control of molecular weight and end-groupfunctionality.

U.S. Pat. No. 3,374,277 teaches crystalline, high-melting isobutyleneoxide diols having a molecular weight of 500 to 20,000. The diols areobtained by the alkyl lithium promoted cleavage of very high molecularweight isobutylene oxide homopolymers. The predominantly head-to-tailarrangement of the isobutylene oxide units in the high molecular weighthomopolymers and the mechanism of cleavage result in the diol productshaving approximately 50% tertiary hydroxyl end-groups and 50% primaryhydroxyl end-groups. It is well-known that tertiary hydroxyl groups aremuch less reactive towards electrophilic functional groups such asisocyanates than are primary or secondary hydroxyl groups. Thus, theisobutylene oxide diols taught by this reference would be difficult toincorporate into polyurethane using conventional methods and techniques,since chain extension will be slow compared to polyols containingpredominantly primary or secondary hydroxyl end-groups. Furthermore,precise control of molecular weight and molecular weight distribution isdifficult using this method due to the random nature of the cleavageprocess. Isobutylene oxide polyols having a functionality (averagenumber of hydroxyl groups per polymer chain) higher than two cannot beprepared by the process taught in this reference.

EP No. 173,879 teaches polyether polyols having an internal block of amono-substituted alkylene oxide such as propylene oxide and an end-capconsisting of a limited number of isobutylene oxide monomer units. Thesepolyols have only tertiary hydroxyl end-groups, which, for the reasonsdiscussed previously, are normally undesirable when formulatingpolyurethanes.

An object of the present invention is to provide isobutylene oxidepolyether polyols which cannot be made by prior processes.

More specifically, an object of the invention is to provide polyetherpolyols having internal blocks comprised of either isobutylene oxide ora random mixture of isobutylene oxide and a mono- or unsubstitutedalkylene oxide and having one or more endcaps of a mono- orunsubstituted alkylene oxide to provide primary or secondary hydroxylgroups reactive with electrophilic functional groups.

A further object of the invention is to provide a process for producingsuch isobutylene oxide polyether polyols which is relatively straightforward and permits good control of polyol molecular weight, molecularweight distribution, composition, functionality, and physical andchemical properties.

SUMMARY OF THE INVENTION

The present invention provides a polyether comprised of from about 10 to90 mole percent of isobutylene oxide and from about 90 to 10 molepercent of an alkylene oxide selected from the group consisting ofethylene oxide and mono-substituted alkylene oxides, wherein thepolyether has at least one hydroxyl end-group, the hydroxyl end-group isprimary, secondary, or tertiary and the ratio ##EQU1## is greater thanabout 0.50.

Additionally, the present invention provides a process for producingsuch a polyether comprising the steps of (a) polymerizing isobutyleneoxide or a mixture of isobutylene oxide and first portion of an alkyleneoxide selected from the group consisting of ethylene oxide andmono-substituted alkylene oxides in the presence of a crown ether, anactive hydrogen-containing initiator, and an amount of an alkali metaleffective to form an intermediate polymer having at least one hydroxy oralkoxy end-group and (b) reacting the intermediate polymer and a secondportion of an alkylene oxide selected from the group consisting ofethylene oxide and mon-substituted alkylene oxides to form thepolyether.

DETAILED DESCRIPTION OF THE INVENTION

Isobutylene oxide is a di-substituted alkylene oxide, having two methylgroups attached to the same carbon. As a result of this structure, anisobutylene oxide homopolymer of reasonably high molecular weight is ahighly crystalline thermoplastic having a melt temperature of 160°-170°C. In contrast, mono-substituted alkylene oxides such as propylene oxidehomopolymerize using base or acid catalysis yield to yield amorphouspolyethers with low (-50° to -80° C.) glass transition temperatures.Therefore, random copolymers of isobutylene oxide and a mono-substitutedalkylene oxide would be expected to exhibit properties intermediatebetween those displayed by the homopolymers of each monomer. By varyingthe relative proportions of the two monomers, the properties may beadjusted to meet the requirements of particular applications.

For example, it is well-known that the strain-induced crystallizationexhibited by certain polyether polyols such as poly(tetrahydrofuran)contributes to improved tensile properties when the polyols areincorporated into polyurethanes or other segmented elastomers. However,to function effectively as a rubbery soft segment in the segmentedelastomer, the polyol should not be highly crystalline. Randomcopolymers of isobutylene oxide and a less substituted alkylene oxide,the crystallinity of which may be altered by varying the amount of mono-or unsubstituted alkylene oxide used, therefore are expected to provideunique properties in a segmented elastomer which cannot be obtainedusing either isobutylene oxide homopolymer diols or mono- orunsubstituted alkylene oxide homopolyols.

However, to be useful as a segmented elastomer intermediate, a polyolmust have hydroxyl end-groups which are sufficiently reactive withelectrophilic functional groups under normal processing conditions topermit chain extension. Polyol chain ends which are not reacted withelectrophilic functional groups not only limit the molecular weight ofthe segmented elastomer formed but also disrupt the phase separation ofthe elastomer. Relatively high molecular weight and complete phaseseparation are both necessary to develop optimum physical properties.

The novel polyether polyols of this invention are comprised of aninternal block and at least one end-cap which provides a primary orsecondary hydroxy group reactive with an electrophilic functional groupsuch as an isocyanate. The internal block is comprised of eitherisobutylene oxide or a mixture of isobutylene oxide and a lesssubstituted alkylene oxide. The end-cap is comprised of ethylene oxideor a mono-substituted alkylene oxide. Examples of suitablemono-substituted alkylene oxides include propylene oxide, 1,2-butyleneoxide, allyl glycidyl ether, and phenyl glycidyl ether. The mono- orunsubstituted alkylene oxide in the end-cap(s) may be the same as ordifferent from the mono- or unsubstituted alkylene oxide in the internalblock. Mixtures of mono- or unsubstituted alkylene oxides may be used.The polyether as a whole may be comprised of from about 10 to 90 molepercent of isobutylene oxide and from about 90 to 10 mole percent of themono- or unsubstituted alkylene oxide(s). In a preferred embodiment, thepolyether is comprised of from about 25 to 75 mole percent isobutyleneoxide and from 75 to 25 mole percent of propylene oxide and has at leasttwo hydroxyl end-groups.

The polyether polyols may be of any suitable molecular weight. Forpolyurethane applications, the number average molecular weight preferredwill be from about 250 to 10,000. Most preferably, the molecular weightwill range from about 500 to 6,000. The relative molecular weights ofthe internal block and the end-cap(s) can vary, but in general it ispreferred that the internal block containing the isobutylene oxidecomprise the majority by weight of the total polyol. The relativeproportion of the internal block and the end-cap(s) should be such thatthe ratio of ##EQU2## is at least about 0.50. Higher ratios arepreferred in order to obtain a polyol which is more highly reactivetowards electrophilic functional groups. It may be difficult to achievequantitative end-capping (i.e., a ratio of 1.00). However, polyols withratios of from about 0.60 to 0.90 are generally satisfactory for use assegmented elastomer components.

The polyether polyols of this invention may be linear or branched.Branching may be introduced by the use of an active hydrogen-containinginitiator having a functionality greater than two or by the introductionof a multi-functional monomer such as a diepoxide during thepolymerization to link growing polyol chains together. Althoughpreferably the internal block has a substantially random structure whenthe isobutylene oxide is copolymerized with another alkylene oxide, itmay be desirable to vary the sequence of the monomer units to alter theproperties of the resulting polyether polyol. For example, the internalblock may itself contain smaller blocks in which the relativeproportions of isobutylene oxide and the alkylene oxide are varied.Methods of accomplishing such variations will become apparent from thedescription of the preferred process used for the preparation of thepolyols.

Although the polyether polyols of this invention contain at least onehydroxyl end-group per polymer chain, the average functionality of theproduct may be increased as desired. Polyols having an averagefunctionality of two (diols) of three (triols) are most preferred,particularly for polyurethane applications. Small amounts of monol maybe present in a polyol having a theoretical functionality of two or moredue to the tendency of the alkylene oxides to isomerize to allylicalcohols under basic conditions. The allylic alcohols can serve ascompeting initiators.

The process for the preparation of the polyether polyols of thisinvention involves a first step in which isobutylene oxide is eitherhomopolymerized or copolymerized with a mono- or unsubstituted alkyleneoxide in the presence of an active hydrogen-containing initiator, analkali metal, and a crown ether.

The active hydrogen-containing initiator may be any of the compoundsknown in the art to be suitable for the preparation of conventionalpolyether polyols by base catalysis. Examples of preferred initiatorsinclude alcohols such as methanol, isopropyl alcohol, and1,2-pentanediol, water, vicinal glycols such as ethylene glycol,propylene glycol, and pinacol, glycol oligomers such as diethyleneglycol, tripropylene glycol, and other low molecular weight alkyleneoxide oligomers, as well as trifunctional compounds such as trimethylolpropane, glycerin, and their alkoxylated derivatives. Amines, phenols,and thiols may also be useful initiators. The type of initiator used isnot critical, although the average functionality of the polyether polyolproduct will be largely determined by the functionality of the initiatoremployed. The initiator should be capable of forming a salt with analkali metal. The number average molecular weight of the polyetherpolyol will depend on the relative amounts of alkylene oxide andinitiator in accordance with the following formula: ##EQU3##

The alkali metal may be any of the alkali metals which effectivelycatalyze the polymerization of alkylene oxides. Potassium and sodium areparticularly preferred. The alkali metal may be derived from anysuitable source, including alkali metal hydroxides, alkoxides,phenoxides and the like. The alkali metal itself (for example, a sodiummetal dispersion) may be used. In a preferred embodiment, an alkalimetal hydroxide is combined with the initiator prior to polymerizationand reacted to form an alkoxide (the alkali metal salt of theinitiator). It is desirable to remove the water formed in this reaction;suitable methods include azeotropic distillation and vacuum stripping.The amount of alkali metal used can be varied as desired, with the rateof polymerization being generally dependent on the alkali metalconcentration. The mole ratio of alkali metal to active hydrogen in theinitiator preferably varies from about 1:100 to 2:1. Most preferably,the ratio is between about 1:20 and 1:2.

The crown ether is used as a cocatalyst with the alkali metal and servesto greatly increase the rate of polymerization. Due to itsdisubstitution, isobutylene oxide is difficult to polymerize to anyappreciable molecular weight with retention of theoretical functionalityusing an alkali metal alone since the rate of chain growth relative tothe rate of isobutylene oxide isomerization to methallyl alcohol is notfavorable. Without the crown ether, unacceptably high levels ofunsaturation, reflecting a high proportion of monol, are produced in thepolyether polyol product if reaction temperatures sufficient to causereasonably rapid monomer conversion are used.

Suitable crown ethers include any of the macrocyclicheteroatom-containing ligands known to complex with alkali metals. Ingeneral, such crown ethers may be represented by the structural formula:##STR1## where n is an integer from 4 to 10, each R and R' taken aloneor in combination are hydrogen, aryl, or alkyl, and R and R' in any orall of the n units may be joined together to form a benzene orcycloalkane ring of 5 to 7 members, and X is sulfur, oxygen, or tertiaryamino group. The identity of X in the n units may vary (i.e., a crownether may contain oxygen as well as sulfur). In addition, any of the nunits may have move than two carbon atoms between the X heteroatoms.Carbonyl groups may also be present in the macrocycle. Bicycliccompounds having nitrogen bridgehead atoms and having in the hydrocarbonbridging chains at least two additional heteroatoms selected from thegroup consisting of oxygen, sulfur, and tertiary amino are also suitablefor use as the crown ether in the process of this invention. Suchbicyclic compounds are sometimes referred to as "cryptates". Specificexamples of suitable and readily available crown ethers include12-crown-4, 15-crown-5, 18-crown-6, 21-crown-7, dibenzo-18-crown-6,2.2.2-cryptate, and dicyclohexano-18-crown-6. Mixtures of crown ethersmay be used. Polymer- or substrate-bound crown ethers are also suitablefor use in the process of this invention. Substrate-bound crown ethersmay be prepared using an insoluble inorganic substrate such as aluminaor silica gel, as described in Bradshaw, et al J. Org. Chem 53,3190(1988) and Bradshaw, et al J. Chem Soc., Chem Commun. 812 (1988). Anexample of a polymer-bound crown ether is the condensation product offormaldehyde and dibenzo-18-crown-6, which is available commerciallyfrom Fluka Chemical. Additional polymer-bound crown ethers suitable foruse in the process of this invention are described in Blasius, et al J.Chromatography 201, 147 (1980). The use of a polymer- or substrate-boundcrown ether will facilitate the recovery of the crown ether from thefinal polymerization reaction mixture.

The molar ratio of crown ether to alkali metal can vary from about 1:50to 5:1, with the range of 1.5:1 to 1:4 being preferred. A 1:1 molarstoichiometry is most preferred in order to obtain an optimum rate ofpolymerization with a minimum amount of alkylene oxide isomerization.

Typically, the polymerization of the alkylene oxide(s) is carried out ata temperature of from about 30° to 120° C. In general, higher reactiontemperatures will result in increased rates of monomer conversion andpolymerization while lower temperatures will decrease the amount ofunsaturation in the polyol product. For these reasons, the preferredpolymerization temperature range is from 50° to 80° C. Depending on thetemperature and the volatility of the monomer(s) employed, the reactionpressure may be atmospheric, subatmospheric, or above atmospheric.

It may be advantageous to carry out the polymerization of the alkyleneoxide(s) in the presence of an inert solvent to dissolve or to reducethe viscosity of the polyol product. This is particularly desirable whenpreparing a polyol having a high isobutylene oxide content at relativelylow temperature, since such a product may tend to solidify in theabsence of solvent. Aromatic hydrocarbons such as toluene and etherssuch as tetrahydrofuran are examples of suitable solvents. Bulkpolymerization may be used when the polyol product is substantiallyliquid at the reaction temperature. It is preferred that the polyolreaction mixture be stirred and that the monomer(s) be added in acontinuous fashion to the mixture.

After polymerization of the isobutylene oxide, alone or in combinationwith a less-substituted alkylene oxide, to form the internal block, theintermediate polymer is reacted with ethylene oxide or amono-substituted alkylene oxide to yield an end-capped polyether polyol.The mono-substituted alkylene oxide may be the same as or different fromthe comonomer in the internal block. Propylene oxide is the preferredalkylene oxide to be used in the end-capping step.

In general, the reaction conditions employed during the end-capping stepmay be the same as those used to form the internal block. Removal of anysmall amounts of isobutylene oxide remaining after formation of theinternal block prior to the end-capping step is preferred.

The amount of ethylene oxide or mono-substituted alkylene oxide to beadded to produce the end-cap will vary depending upon the molecularweight and functionality of the intermediate polymer. However, in orderto obtain a polyether polyol product having terminal hydroxyl groupswhich are at least 50% primary and/or secondary, generally at leastabout 5 equivalents of the alkylene oxide per equivalent of hydroxylend-group is preferably used. A higher ##EQU4## ratio can be achieved byincreasing the equivalents of alkylene oxide used.

After the end-capping step, the crude polyether polyol may be strippedto remove any remaining unreacted alkylene oxide and then treated toseparate the alkali metal and crown ether from the product. Any methodknown in the art for neutralizing a polyether polyol prepared using basecatalysis is suitable, including water-washing and acid precipitation.

It has been found that contacting the crude polyol with an adsorptionagent such as magnesium silicate effectively reduce the alkali metal andcrown ether content of the product to acceptable levels. Typically, fromabout 1 to 5 parts by weight of the adsorption agent are contacted with100 parts by weight of the polyol for about 1 to 5 hours at atemperature of from about 90° to 130° C. The treated polyol is thenfiltered to remove the adsorption agent containing the alkali metal andcrown ether.

Because the polyether polyols of this invention can have two or moreterminal hydroxyl groups per polyol chain, the majority of which areprimary and/or secondary, they may be used in various chain extensionreactions to form useful high molecular weight polymer products. Thesenovel polyether polyols are suitable for use in any of the chainextension reactions in which conventional polyether polyols are employedand which are well-known to those skilled in the art. The chainextension agent can be a polyfunctional compound containingelectrophilic functional groups which react under appropriate conditionsof temperature, pressure, and catalyst with the hydroxyl groups of thepolyol. Such agents include di- or polyisocyanates, di- orpolyanhydrides, and di- or polyepoxides. Useful polyester and polyamideblock copolymers may also be formed with these polyether polyols usingany of the known condensation polymerization techniques. Thus, thepolyether polyols of this invention may serve as intermediates in thepreparation of a wide variety of thermoplastic resins, thermoset resins,elastomers, foams and the like.

The polyether polyols of this invention may also find utility assurfactants, dispersing agents, foam stabilizers, adhesives, andfunctional fluids.

The invention is further illustrated, but not limited, by the followingexamples.

EXAMPLES Preparation of Isobutylene Oxide Polyols - General Procedure

Isobutylene oxide (BASF) was purified by fractional distillation fromcalcium hydride through a 12" column packed with 1/8 glass helices.Propylene oxide (ARCO Chemical) was purified by distillation fromcalcium hydride. 18-Crown-6 (Aldrich) was purified by recrystallizationfrom acetonitrile.

In general, the polymerizations were performed in a multi-neck roundbottom flask equipped with reflux condenser, addition funnel, mechanicalstirrer, nitrogen bubbler, and heating mantle. Crown ether, initiator,potassium hydroxide, and toluene were charged to the flask and waterremoved by azeotropic distillation using a Dean-Stark trap. In examplesperformed without solvent, the remaining toluene was then removed underreduced pressure. Isobutylene oxide or a mixture of isobutylene oxideand propylene oxide were added to the stirred mixture while maintaininga constant internal temperature (Step 1). The rate of addition wasadjusted so that vigorous refluxing of unreacted epoxide was avoided.After addition was completed (generally ca. 8-12 hours), the mixture washeated for at least another 12 hours.

Any unreacted epoxide was then removed under reduced pressure andpropylene oxide added to end-cap the polyol (Step 2). After reacting atleast 12 hours, the product was stripped again and treated with 4%magnesium silicate (Magnesol®, a product of the Reagent Chemical Co.),0.5% water, and 1% diatomaceous earth filter-aid (Celite Filter Aid®, aproduct of the Johns Manville Co.) for 4 hours at 110° C. to removepotassium hydroxide and crown ether. The polyol was then filteredthrough diatomaceous earth filter-aid at 70° C., diluted further withtoluene, and treated with 500 ppm BHT. In most cases, the toluenesolution was also washed with water several times to assure completecatalyst removal, although this did not appear to be necessary. Thefinal polyol was obtained by vacuum stripping to remove solvent andwater.

The exact reaction conditions and quantities of reactants used in eachexample are given in Table I, as well as the analytical data obtainedfor each product. The polyether polyols were characterized byconventional analytical methods. Gel permeating chromatography wasconducted using polypropylene glycol calibration standards. Thecomposition of the polyols (% PO, %IBO) was determined by ¹³ C nuclearmagnetic resonance. The ratio ##EQU5## was assumed to be equal to##EQU6## where the calculated hydroxyl number is equal to ##EQU7## Thewet chemical method used to measure hydroxyl number did not detecttertiary hydroxyl groups.

Example 1 demonstrates the preparation of a triol using a propoxylatedglycerin initiator and a 1:1 molar ratio of 18-crown-6 and potassiumhydroxide. All of the propylene oxide was added in step 1, yielding apolyol in which nearly all of the hydroxyl end-groups were tertiary.

Examples 2 and 3 also illustrate the preparation of a triol using apropoxylated glycerin initiator, but in these examples the polyols wereend-capped with propylene oxide. Approximately 70-80% of the hydroxylgroups in the final products were primary and/or secondary. Relativelylow levels of unsaturation were observed.

Examples 4-8and 10-11 demonstrate the preparation of diols havingmolecular weights of about 2000 in which the internal blocks containfrom about 68 to 100 weight percent isobutylene oxide. Each diol wasend-capped with propylene oxide to provide polyols in which the majorityof the hydroxyl groups are primary and/or secondary. The low levels ofunsaturation indicate that the functionalities of the polyols are closeto the expected value of 2.0. The diols containing high amounts (95-100percent) of isobutylene oxide in the internal block were waxy solids,while the diols containing less isobutylene oxide were substantiallyliquid at room temperature.

The diol of Example 8was used in the preparation of cast urethaneelastomers as described below.

Example 9 is a comparative example in which an isobutyleneoxide/propylene oxide polyol was prepared without the use of a crownether cocatalyst. Even after a total reaction time of 37.5 hours at atemperature of 110° C., only 70% conversion of the monomers wasachieved. The unsaturation level of the product was 0.256 meg/g,considerably higher than that observed for polyethers of similarcomposition prepared using a crown ether cocatalyst. The functionalityof the product was therefore significantly less than the expected valueof 2.0. The molecular weight as measured by GPC was also much lower thanexpected.

                                      TABLE I                                     __________________________________________________________________________     PREPARATION OF ISOBUTYLENE OXIDE POLYOLS                                     __________________________________________________________________________              EXAMPLE #                                                                     1     2      3     4       5       6                                __________________________________________________________________________    Initiator A     B      A     1,4-Butanediol                                                                        1,4-Butanediol                                                                        1,4-Butanediol                   g         48.0  76.36  48.0  12.29   12.29   12.29                            moles     0.10  0.0429 0.10  0.136   0.136   0.136                            85% KOH, g                                                                              1.98  1.98   1.98  1.98    1.98    1.98                             18-Crown-6, g                                                                           8.39  7.93   7.93  7.93    7.93    7.93                             Step 1                                                                        IBO, g    123.08                                                                              135.11 101.24                                                                              148.50  66.25   113.97                           wt. %     49.0  74.5   100   100     100     68                               PO, g     127.93                                                                              46.36  --    --      --      40.38                            wt. %     51.0  25.5   --    --      --      24                               Mn, calc. 2990  6010   1490  1180    580     1220                             Step 2                                                                        PO, g     --    48.37  159.84                                                                              225.41  223.10  136.93                           Mn, calc. --    7140   3090  2840    2220    2230                             Solvent (g)                                                                             --    --     --    THF (20)                                                                              Toluene (43)                                                                          Toluene (43)                     Temp., °C.                                                                       50    50→90                                                                         50→75                                                                        60→80                                                                          70      60                               Yield, g, calc.                                                                         299.01                                                                              306.20 309.08                                                                              386.20  301.64  303.57                           Found     n.d.  268.52 265.38                                                                              284.94  294.43  252.66                           Mn (based on                                                                            --    6260   2650  2100    2170    1860                             yield)                                                                        Hydroxyl #                                                                              n.d.  21.4   46.1  45.8    46.2    47.6                             Found                                                                         Calc.     n.d.  26.9   63.5  53.6    51.7    60.3                             Mn, GPC   1760  3430   2220  1590    1580    1510                             Mw/Mn, GPC                                                                              1.18  1.64   1.21  1.24    1.24    1.20                             Viscosity, cps                                                                          660 (25° C.)                                                                 1240 (50° C.)                                                                 900 (25° C.)                                                                 Wax     490 (25° C.)                                                                   550 (25° C.)              Mole % PO, Calc.                                                                        56    55     64    58      74      58                               Found     90    85     58    70      78      67                               Mole % IBO, calc.                                                                       41    44     33    39      22      38                               Found     10    15     42    30      22      33                               Unsat., meq/g                                                                           0.023 0.100  0.039 0.051   0.043   0.043                            K, ppm    16    <2     <2    <2      <2      <2                               1° + 2° hydroxyl                                                          --    0.80   0.73  0.85    0.89    0.80                             total hydroxyl                                                                __________________________________________________________________________              EXAMPLE #                                                                     7        8       9.sup.c 10       11                                __________________________________________________________________________    Initiator 1,4-Butanediol                                                                         TPG     TPG     1,4-Butanediol                                                                         1,4-Butanediol                    g         14.34    174.5   54.95   26.63    26.63                             moles     0.159    0.909   0.286   0.295    0.295                             85% KOH, g                                                                              1.98     11.31   3.34    3.29     3.29                              18-Crown-6, g                                                                           7.93     45.31   --      13.19    13.19                             Step 1                                                                        IBO, g    131.08   731.6   220     328.96   346.92                            wt. %     69       80      79      100      95                                PO, g     45.32    181.8   57      --       18.31                             wt. %     24       20      21      --       5                                 Mn, calc. 1200     1200    1200    1200     1330                              Step 2                                                                        PO, g     166.02   925.7   279     305.96   293.60                            Mn, calc. 2240     2220    2210    2240     2320                              Solvent (g)                                                                             --       --      --      Toluene  --                                                                   (50→150)                            Temp., °C.                                                                       60       60      110     60→80                                                                           60→70                      Yield, g, calc.                                                                         356.76   2013.6  611     661.55   685.46                            Found     307.22   1828.9  428     n.d.     655.57                            Mn (based on                                                                            1930     2010    1550    --       2220                              yield)                                                                        Hydroxyl #                                                                              43.4     42.6    47.0    42.8     34.5                              Found                                                                         Calc.     58.1     55.8    72.4    n.d.     50.5                              Mn, GPC   1540     1610    560     1480     1730                              Mw/Mn, GPC                                                                              1.24     1.30    1.43    1.31     1.23                              Viscosity, cps                                                                          686 (25° C.)                                                                    700 (25° C.)                                                                   390 (25° C.)                                                                   Solid    Solid                             Mole % PO, Calc.                                                                        59        64     60      48       53                                Found     63       63      55      49       39                                Mole % IBO, calc.                                                                       37       36      40      52       47                                Found     37       37      45      51       61                                Unsat., meq/g                                                                           0.044    0.043   0.256   0.035*   n.d.*                             K, ppm    <2       <2      n.d.    <2       <2                                1° + 2° hydroxyl                                                          0.75     0.76    0.65    n.d.     0.68                              total hydroxyl                                                                __________________________________________________________________________     NOTES TO TABLE I                                                              *not completely soluble during analysis                                       A = polypropylene glycol triol (propoxylated glycerin, MW = 480)              B = polypropylene glycol triol (propoxylated glycerin, MW = 1780)             TPG = tripropylene glycol                                                     n.d. = not determined                                                         c = comparative example                                                  

Preparation of Cast Urethane Elastomers - General Procedure

The isobutylene oxide polyol of example 8was reacted with MDI [methylenebis-(phenyl isocyanate), purified before use by hot filtration) to forma prepolymer by charging the molten MDI to a 250 mL resin kettleequipped with thermometer and mechanical stirrer, adding the warm polyolby syringe, and reacting the mixture for 4 hours at 120° C. under anitrogen atmosphere. After degassing the prepolymer briefly, the chainextender was added. When ethylene glycol was used as a chain extender,13 ppm (based on total weight of the formulation) T-12® catalyst (aproduct of M&T Chemical) was added with the chain extender. The mixturewas stirred vigorously until it turned opaque and more viscous(generally 1-15minutes) and then poured into a 1/8"×5"×10" roomtemperature aluminum mold. The plaques were cured in a 120° C. pressunder 10 tons pressure, demolded, and cured overnight (16 hrs.) in a100° C. oven. Details of the preparation appear in Table II. Theproperties of the cast urethane plaques were determined by standard ASTMmethods and are reported in Table II. The NCO index was determined fromthe calculated hydroxyl number of the polyol.

                                      TABLE II                                    __________________________________________________________________________    PREPARATION OF CAST URETHANE ELASTOMERS                                                   Example #                                                                     12      13      14       15                                       __________________________________________________________________________    Polyol      Example 8                                                                             Example 8                                                                             Example 8                                                                              Example 8                                g           98.21   98.71   99.05    98.67                                    Isocyanate  MDI     MDI     MDI      MDI                                      g           52.44   52.44   55.93    55.93                                    Chain-Extender                                                                            1,4-Butanediol                                                                        1,4-Butanediol                                                                        Ethylene Glycol                                                                        Ethylene Glycol                          g           13.57   13.56   9.97     10.02                                    Catalyst (ppm)                                                                            --      --      T-12 ® (13)                                                                        T-12 ® (13)                          Chain Extender                                                                Addition Temp. °C.                                                                 80      80      50       35                                       % Hard Segment                                                                            40.2    40.1    40.0     40.1                                     NCO Index   1.05    1.05    1.06     1.06                                     Hardness    88 (A)  88 (A)  88 (A)   88 (A)                                   Tensile Strength                                                                          2270    2380    2370     2430                                     100% Modulus                                                                              1210    1200    1320     1280                                     300% Modulus                                                                              1840    1830    2160     2060                                     % Elongation                                                                              430     490     343      383                                      Comp. Set (70° C.), %                                                              37      36      29       32                                       Tear Strength                                                                             370     380     399      402                                      % Rebound   36      41      41       36                                       Flex Stress (5% Strain)                                                                   210     240     213      271                                      Tg, °C. (DMA)                                                                      -16     -3      --       --                                       (DSC)       -27     -28     -26      -22                                      __________________________________________________________________________

I claim:
 1. A high molecular weight polymer product comprising thereaction product ofa) a chain extension agent selected from the groupconsisting of diisocyanates, polyisocyanates, dianhydrides,polyanhydrides, diepoxides, and polyepoxides; and b) a polyester polyolcomprised ofi) an internal block of isobutylene oxide and, optionally, afirst less substituted alkylene oxide selected from the group consistingof ethylene oxide and mono-substituted alkylene oxides; and ii) at leasttwo end-caps of a second less substituted alkylene oxide selected fromthe group consisting of ethylene oxide and mono-substituted alkyleneoxides, which may be the same as or different from the first lesssubstituted alkylene oxide; wherein the amount of isobutylene oxide inthe polyether polyol as a whole is from about 10 to 90 mole percent andthe total amount of first and second less substituted alkylene oxide isfrom about 10 to 90 mole percent, the polyether polyol has at least twohydroxyl end-groups, the hydroxyl end-groups are primary, secondary, ortertiary, and the ratio ##EQU8## is greater than about 0.50.
 2. The highmolecular weight polymer product of claim 1 wherein the chain extensionagent is a diisocyanate.
 3. The high molecular weight polymer product ofclaim 1 wherein the chain extension agent is a polyisocyanate.
 4. Thehigh molecular weight polymer product of claim 1 wherein the polyetherpolyol has two hydroxl end-groups.
 5. The high molecular weight polymerproduct of claim 1 wherein the first and second less substitutedalkylene oxides are each propylene oxide.
 6. The high molecular weightpolymer product of claim 1 wherein the number average molecular weightof the polyether polyol is from about 500 to 6,000.
 7. The highmolecular weight polymer product of claim 1 wherein the amount ofisobutylene oxide in the polyether polyol as a whole is from about 25 to75 mole percent and the total amount of first and second lesssubstituted alkylene oxide in the polyether polyolis from about 25 to 75mole percent.
 8. The high molecular weight polymer product of claim 1wherein the ratio ##EQU9## in the polyether polyol is from about 0.60 to0.90.
 9. A polyurethane comprising the reaction product ofa) a chainextension agent selected from the group consisting of diisocyanates andpolyisocyanates; and b) a polyether polyol having a number averagemolecular weight of from about 500 to 6,000 which is comprised ofi) aninternal block of isobutylene oxide and, optionally, propylene oxide;and ii) at least two end-caps of propylene oxide; wherein the amount ofisobutylene oxide in the polyether polyol as a whole is from about 25 to75 mole percent and the total amount of propylene oxide is from about 25to 75 mole percent, the polyether polyol has at least two hydroxylend-groups, the hydroxyl end-groups are primary, secondary, or tertiary,and the ratio of primary +secondary total hydroxyl is greater than about0.50.
 10. The polyurethane of claim 9 wherein the polyether polyol hastwo hydroxyl end-groups.
 11. The polyurethane of claim 9 wherein thepolyether polyol has three hydroxl end-groups.
 12. The polyurethane ofclaim 9 wherein the chain extension agent is a diisocyanate.
 13. Thepolyurethane of claim 12 wherein the diisocyanate is methylenebis(phenyl isocyanate).
 14. The polyurethane of claim 9 wherein theratio ##EQU10## in the polyether polyol is from about 0.60 to 0.90.